Chemical aids used to remove dispersed oil and/or solids from water are commonly referred to as water clarifiers, reverse emulsion breakers, deoilers, coagulants, flocculants and/or coalescence aids. In the oil and gas industry, after the initial separation of the bulk produced fluids (e.g., crude oil), the produced water still contains finely dispersed solids and oil. These oil and solids particles are well stabilized and are difficult to separate by means of physical settling alone. Often, such produced water cannot be reused nor disposed of as is and it is therefore necessary to find appropriate solutions to do so. Regulations around the world generally limit the oil and grease content in produced water to a maximum of 15 parts-per-million (ppm) to 50 ppm for discharge into the environment (Arnold, K.; Stewart, M. Surface Production Operations; 3rd ed.; Elsevier/Gulf: Boston, 2008, 483). The water is thus treated to meet regulatory, environmental, and operational goals.
A range of synthetic water soluble cationic polymers are known to separate oil/solid particles from produced water. Poly(diallyl dimethylammonium chloride), copolymers of acrylamide or alkyl acrylates with various cationic co-monomers are known as water clarifiers. Chemical treatment of the produced water involves the addition of a few ppm levels of inorganic salts and/or organic polymers to facilitate the separation through coagulation and floc formation. Organic polymers (ionic or neutral) can be more effective than the inorganic salts and results in water with minimum oil/solid residues.